Bulls for Succos

On the first day of Succos 13 bulls were brought with the Korban Musaf.  On each following day they brought one less bull.  Since this was Eretz Yisrael there were only 7 days of Succos. 

Question: How many bulls were brought in total? (Bamidbar 29: 12-34)

Answer: 

Day One:  13

Day Two: 12

Day Three: 11

Day Four: 10

Day Five: 9

Day Six: 8

Day Seven: 7

Total:  70